174 PRESSURE UPON THE SIDES OF VESSELS. 



manner, proves that the liquid exerts no. upward 

 pressure against the sides. That there is no downward 

 pressure is shown by placing a weight in the scale-pan 

 on the right-hand side ; the cylinder will be immediately 

 lifted from the plate and the water will escape. The 

 weight necessary for this will be about 2 or 3 gr , if the rim 

 has been oiled, and 7 or 8 gr if a weight of 5^ was used 

 on the left-hand side for pressing the cylinder against 

 the plate. The vessel 2 is now balanced in the same 

 manner; no oil or weight is required for preventing the 



escape of water ; a light pressure 

 with the hand, while the water 

 is poured in, is sufficient. When 

 full, the downward pressure of 

 the water against the sides is so 

 great that a weight of 20 gr or 

 more may be placed in the scale- 

 pan on the right without lifting 

 the sides of the vessel from the 

 base. The vessel 3 is not sus- 

 pended, but simply placed upon 

 the plate, against which it presses 

 with its own weight. It can only 

 be filled with water up to a cer- 

 tain height; if more water is 

 added, the upward pressure of 



^ Q ^^ aga i nst tne sides is ' 



sufficient to raise them above the plate, thus allowing , 

 the water to escape. In doing so the vessel tends to 

 glide laterally from the plate. To prevent its falling 

 and breaking, the left hand must be ready to seize it. 

 For the experiments on the pressure upon the base 



